The present invention relates to a method and apparatus for measuring the height of the surface of an object. More particularly, the present invention relates to such a measuring method suitable for measurement of the height of a spherical object such as, for example, a solder bump formed on an electronic component such as a TAB (Tape Automated Bonding) and a semiconductor module such as an LSI, and furthermore the present invention relates to a measurement method of the height of an apex of a spherical object which is not positioned strictly and has a surface state which is not stabilized due to minute ruggedness or discoloration.
In the CCB bonding or the like, a large number of minute spherical solder bumps formed on an electronic component such as an LSI in the form of lattice are joined as electrodes. Accordingly, in order to ensure the reliability of connection, it is indispensable to inspect the height of all of the solder bumps before connection. Thus, it is necessary to measure the height of the apex of a spherical object at a high speed and with high accuracy.
Heretofore, there are known various methods of measuring the height of an object without contact therewith by means of the triangular surveying method using an optical beam. Of such methods, as a method of measuring the height of the apex of an object to be measured in case where the object is spherical and is not positioned strictly, that is, in case where the position of the apex of the object is not known exactly, there is a method in which X, Y and Z axes of the three-dimensional orthogonal coordinates are set and an optical beam is scanned relatively in the X-axis direction of the object as shown in FIG. 8A (801), so that a position of an inflection point on the scanned line is obtained from a quantity of reflected light of the optical beam by means of a method described later, the relative scanning operation of the optical beam being made in the Y-axis direction including the inflection point (802), so that a position of an inflection point on the scanned line is obtained from a quantity of reflected light similarly and this position is defined as a position 803 of the apex of the object as shown in FIG. 8B to thereby decide the height of this place to be the height of the object.
In the above decision method of obtaining the inflection point from the reflected light quantity, a center position between the position where the reflected light quantity exceeds a predetermined decision level and the position where the reflected light quantity is reduced to the decision level or less is decided as the inflection point.
A technique pertinent to the technique of this kind is described in JP-A-60-196608, for example.